Ionization chamber



May 27, 1952 c. J. BORKOWSKI ET AL 2,598,215

IONIZATION CHAMBER Filed Jan. 9, 1946 FTE.E..

Patented May 27, 1952 IONIZATION CHAMBER Casimer J.

Borkowski and Ralph H. Firminhac,

Oak Ridge, Tenn., assignors to the United States of America asrepresented by theUnited States Atomic Energy Commission ApplicationJanuary 9, 1946, Serial No. 640,106 2 Claims. (01. 313-54) The presentinvention relates to radiation measuring apparatus, and moreparticularly to ionization chambers for measuring alpha particleemission.

It is frequently desirable to collect dust particles or the like on arelatively large surface such as a sheet of filter paper, and then to beable to determine the radioactivity as an indication of the activity ofthe dust particles.

An object of the invention is the provision of an ionization chamberwhich will accommodate a large surface sample such as a sheet of filterpaper.

Another object of the invention is to provide an alpha counting chamberhaving substantially fifty percent geometry.

Other objects and advantages of the invention will become apparent fromthe following description, when read in connection with the accompanyingdrawing, wherein is illustrated a preferred embodiment of the invention.

In the drawing,

Fig. 1 is a side view in section of an ionization chamber constructed inaccordance with the invention; and

Fig. 2 shows diagrammatically one suitable connection to apre-amplifier.

The ionization chamber shown to illustrate the invention comprises aright cylindrical container In having its lower end screw threaded toreceive a removable end disc II, and having its upper portionpartitioned off by a wall l2 to form a compartment suitable forreceiving a pre-amplifier tube or the like. The upper face of the discII has secured thereto a shouldered block [3 of insulating materialwhich supports, in coaxial relation in the container ill, a cylindricaltube M which becomes the high voltage electrode when connected asdescribed below. A central rod-like collecting electrode I5 is supportedby the partition I2 to extend along the axis of the high voltageelectrode M.

The base of the high voltage electrode M has secured thereto a springcontact member I6, which is adapted to make wiping contact with a highvoltage lead ll extending through the Wall of the container l0 andsuitably supported by an insulator [8. With this arrangement, the

high voltage is not applied to the electrode I4 until it is safely inposition and the high voltage is removed when the disc II is unscrewedfor removal. In order to prevent sparking due to accidental contactbetween the high voltage electrode l4 and the lead I! during insertionand removal a sleeve [9 of insulating material, such 2 as rubber, isprovided around the high voltage electrode 4.

By unscrewing the end disc II, the high voltage electrode HZ may beeasily removed from the interior of the container H3, and a sheet 20 ofpaper or foil may be curled and inserted inside the hollow electrode is,thereby giving maximum geometry of approximately fifty percent forcounting alpha emission from the paper or foil 20 when the electrode I4is returned to the position shown in the drawing.

Anyone skilled in the art can readily devise a suitable circuit forcounting the alpha emission from the sheet 28. One suitable circuit isindicated in Fig. 2. a

While for the purpose of illustrating the invention a preferredembodiment thereof has been described in detail, it is to be understoodthat the invention is not limited thereto but is of the scope of theappended claims.

We claim:

1. An ionization chamber including a container having therein a tubularhigh voltage electrode, a rod collecting electrode extending along theaxis of the tubular electrode, the container having a removable end wallengaging one end thereof in screw-threaded relation to facilitate readyremoval of said tubular electrode, the tubular electrode being mountedthereon and removable therewith, the tubular electrode in operativeposition normally extending upwardly from the removable end wall to forma specimen holder for a tubular specimen contaminated withradioactivity, holding said specimen therewithin to surround said rodelectrode, thereby providing improved chamber geometry.

2. An ionization chamber for counting radioactive foils, filter papers,and the like which can be formed into tubular specimens, comprising acylindrical container threaded at one end to receive a removable endcap; means at the opposite end of said container for mounting a rodcollecting electrode extending coaxially thereof; a specimen holdercomprising a tubular, electrically conductive member mountedperpendicular to and electrically insulated from said end cap, andadapted to receive said specimens at its open end and to hold saidspecimens in tubular configuration against its inner surface, saidspecimens thereby being disposed concentrically about said rod when saidcap is in operative position; a high voltage lead insulated from andcarried by said container and extending inwardly thereof; and a springcontact conductively connected to and carried by said specimen holder,said lead 3 and said contact being so disposed as to make FOREIGNPATENTS firm electrical contact when said cap is in op- Number CountryDate erative assembly and to break contact when said 296 769 GreatBritain 25' 1929 cap is turned for disassembly.

CASIMER. J. BORKOWSKI. 5 OTHER REFERENCES RALPH H. FIRMINHAC. Strong:Procedures in Experimental Physics. 1942 ed., pub1.,by Prentip rHall;New-York, pgs. REFERENCES CITED 1 262 The following references are ofrecord in the. file of this patent: 0

UNITED STATES PATENTS.

Number Name Date 2,197,453 Hassler Apr. 16,- I940 2,440,167 Broxon eta1. A r. 20, 1948 15

